The invention relates to fuel nozzles and, more particularly, to an axial flow fuel nozzle for a gas turbine including a plurality of annular passages to facilitate mixing.
Gas turbine engines generally include a compressor for compressing an incoming airflow. The airflow is mixed with fuel and ignited in a combustor for generating hot combustion gases. The combustion gases in turn flow to a turbine. The turbine extracts energy from the gases for driving a shaft. The shaft powers the compressor and generally another element such as an electrical generator. The exhaust emissions from the combustion gases generally are a concern and may be subject to mandated limits. Certain types of gas turbine engines are designed for low exhaust emissions operation, and in particular, for low NOx (nitrogen oxides) operation with minimal combustion dynamics, ample auto-ignition, and flame holding margins.
In existing low NOx combustor nozzles, a liquid fuel circuit directly injects fuel and water in a recirculation zone (combustion zone). Rich burning of fuel produces high temperatures, which cause the formation of higher emissions. Existing designs also use atomizing air and water together for NOx reduction. It would be desirable to provide a simple design with better liquid fuel atomization in a premixing passage to reduce emissions while also making better use of curtain air.